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Old 02-04-2019, 03:23 PM
 
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If you Google 'foam soffit baffle' you can see some ideas for improving soffit performance. It really depends on what is there now (ridge vents, large gable vent, roof vents, etc).


A friend of mine went nuts a few years ago with radiant barriers (PITA to install unless you are a contortionist), and fans and I think the performance was minimal compared to just insulating.


I think you have to keep in mind that whatever you put in (such as any type of fan) that know for sure you have enough air to actually move.
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Old 02-04-2019, 05:02 PM
 
Location: Scottsdale
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Interesting, thanks Burning.
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Old 02-05-2019, 05:44 PM
 
Location: Phoenix, AZ
2,653 posts, read 3,047,472 times
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Quote:
Originally Posted by veritased View Post
Looking at some research done by building councils in Tucson, turns out that insulating the roof, then sealing the attic, and letting the HVAC ducting cool (or heat in the winter) the attic as it goes from air handler to various rooms, allows a non trivial cost savings. Compared to a traditional vented attic.

Big surprise to me. But I guess the different is in insulation being applied not only above the ceiling, but also on the underside/inside of the rolly some time of expanding foam type of product. That provides a much higher temperature gradient to the attic, and then from there, the leakage of heat from attic to HVAC ducting causes the attic to cool down, and net-net, you save money on the cooling costs to the interior space, as the ceiling is no longer transferring heat to the living space, as the attic is no longer at 160deg F or whatever, it's more like below 100deg F, the studies show.
Your statements are right: the best (but not the least expensive) way to go is to seal up the attic and insulate it with sprayed on foam (especially if your HVAC and ducts are located up there.) Problem is, it's EXPENSIVE, and the return on investment (ROI) will probably not justify you making this upgrade. This would be something to do when the house was originally constructed.

Therefore, I'd recommend that you just add as much attic insulation as you can (blown in), make sure your attic ducts have no leaks or binds in them, and (if possible) install radiant barrier on the underside of your roof. My attic space is SO tight I don't think I can install radiant barrier to the underside of my roof. Again, this SHOULD have been done when the house was built in '91, but builders didn't give a crap about energy efficiency then.
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Old 02-05-2019, 06:23 PM
 
Location: Scottsdale
1,336 posts, read 927,972 times
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OK, I think that is right. I haven't been up there, to take a look, but will when I go for final inspection. Didn't have a ladder on these homes with higher (10ft) ceilings than I am used to.

Not sure I'll be able to install the radiant barrier on the underside of the roof... maybe on top of the blown insulation... if it's cheap enough, worth a try.
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Old 02-07-2019, 09:05 PM
 
Location: Mesa AZ
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I have an exhaust fan on the gable on the north side of my home and the south side gable has a huge shade tree over it so the incoming air is cooler. It runs on a thermostat when I have it switched on. A few times I have forgot to flip the switch in the spring and on the first hot day the house starts heating up much faster until I realize its not on. Many homes have the spinning vents on their roofs, would love to know which way is better. I don't know if I save any money running that fan but I am sure it one of reasons why my heat pump is still running fine after 20+ years and attic fans are cheaper than heat pumps. Some of my neighbors have replaced their roofs twice since I have lived here and I will need to replace my 25 year old roof very soon, I have no doubt the attic fan helped it last that long.

Last edited by Farmer Larry; 02-07-2019 at 09:15 PM..
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Old 02-07-2019, 10:17 PM
 
Location: Scottsdale
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Thanks Farmer Larry. That is a good data point.

When people in AZ have to replace their roofs due to heat, what specifically is failing ?
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Old 02-08-2019, 01:54 AM
 
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To vent or not to vent....



https://m.youtube.com/watch?v=Ld8pzIu45F8
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Old 02-08-2019, 08:12 AM
 
Location: Phoenix, AZ
2,653 posts, read 3,047,472 times
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Quote:
Originally Posted by veritased View Post
OK, I think that is right. I haven't been up there, to take a look, but will when I go for final inspection. Didn't have a ladder on these homes with higher (10ft) ceilings than I am used to.

Not sure I'll be able to install the radiant barrier on the underside of the roof... maybe on top of the blown insulation... if it's cheap enough, worth a try.
It's not recommended to lay the radiant barrier on top of the blown in insulation, reason being that the radiant barrier will eventually get a layer of dust on it. Once that happens, its effectiveness is lost. Installing it right under the roof won't allow it to be coated in dust.
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Old 02-08-2019, 08:42 AM
 
Location: Scottsdale
1,336 posts, read 927,972 times
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I've read that, thanks. It suggests really that the wavelengths heating up the air and housing material reflects less if dust reduces the reflectivity as we as humans think of reflectivity. I wonder if that's really true.
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Old 02-08-2019, 08:56 AM
 
Location: Scottsdale
1,336 posts, read 927,972 times
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Quote:
Originally Posted by Hal Roach View Post
Great video, watching it. Thanks.
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